Magnification compensation and/or beam steering in optical systems

ABSTRACT

Techniques are disclosed for magnification compensation and/or beam steering in optical systems. An optical system may include a lens system to receive first radiation associated with an object and direct second radiation associated with an image of the object toward an image plane. The lens system may include a set of lenses, and an actuator system to selectively adjust the set of lenses to adjust a magnification associated with the image symmetrically along a first and a second direction. The lens system may also include a beam steering lens to direct the first radiation to provide the second radiation. In some examples, the lens system may also include a second set of lenses, where the actuator system may also selectively adjust the second set of lenses to adjust the magnification along the first or the second direction. Related methods are also disclosed.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a continuation of U.S. patent application Ser. No.16/011,564 filed Jun. 18, 2018 and entitled “MAGNIFICATION COMPENSATIONAND/OR BEAM STEERING IN OPTICAL SYSTEMS,” which claims priority to andthe benefit of U.S. Provisional Patent Application No. 62/522,062 filedJun. 19, 2017 and entitled “MAGNIFICATION COMPENSATION AND/OR BEAMSTEERING IN OPTICAL SYSTEMS,” each of which is hereby incorporated byreference in its entirety.

TECHNICAL FIELD

One or more embodiments relate generally to optical systems and moreparticularly, for example, to magnification compensation and beamsteering in optical systems.

BACKGROUND

Projection systems are utilized to project an object at an object planeonto an image plane. In semiconductor technology, lithography systemsmay project a pattern on a mask onto a wafer. In some cases,imperfections may be present between the desired pattern provided by themask and an actual pattern formed on the wafer. While some imperfectionsmay occur randomly, other imperfections may be due to magnificationerror. The magnification error may be different in an x-direction and ay-direction and may be attributed to various sources, such as byimperfect placement of die on a wafer by one or more robots, waferand/or mask expansion (e.g., thermal expansion), settling of compoundsused for moulding the die onto the carrier wafer, and/or other sources.Conventional projection systems may attempt to mitigate magnificationerror by heating and/or cooling the mask or wafer to adjust (e.g., growor shrink) a target image. However, such heating and/or cooling takestime, which adversely affects throughput, and may be impractical formagnification from wafer to wafer. Additionally, heating and cooling cangenerally only apply symmetric compensation, and may be limited by thecoefficient of thermal expansion of the mask or wafer.

SUMMARY

In one or more embodiments, an optical system includes a lens systemconfigured to receive first radiation associated with an object anddirect second radiation associated with an image of the object toward animage plane. The lens system includes a first set of lenses configuredto receive and selectively magnify the first radiation. The lens systemalso includes an actuator system configured to selectively adjust thefirst set of lenses to adjust a magnification associated with the imagesymmetrically along a first direction and a second direction. The lenssystem also includes a beam steering lens configured to direct, based atleast on a tilt of the beam steering lens, the first radiationselectively magnified by the first set of lenses to provide the secondradiation. The tilt of the beam steering lens may be adjustable by theactuator system. The first direction may be orthogonal to the seconddirection. In some cases, the image plane may be parallel to an objectplane. In other cases, the image plane is not parallel to the objectplane.

In one or more aspects, the optical system may also include a lensassembly including a plurality of lenses. The optical system may furtherinclude a first prism configured to pass the first radiation to the lensassembly, where the first set of lenses is configured to pass the firstradiation to the first prism. The optical system may further include amirror configured to receive the first radiation from the first prismvia the plurality of lenses of the lens assembly and reflect the firstradiation. The optical system may further include a second prismconfigured to receive the first radiation reflected from the mirror viathe plurality of lenses of the lens assembly and direct the firstradiation on an optical path toward the image plane.

In some embodiments, the optical system may further include a second setof lenses configured to receive and selectively magnify the firstradiation. The actuator system may be further configured to selectivelyadjust the second set of lenses to adjust the magnification along thefirst direction or the second direction. The beam steering lens may beconfigured to direct, based at least on the tilt of the beam steeringlens, the first radiation selectively magnified by the first set oflenses and second set of lenses to provide the second radiation. Theoptical system may further include a lens assembly including a pluralityof lenses. The optical system may further include a first prismconfigured to pass the first radiation to the lens assembly. The opticalsystem may further include a mirror configured to receive the firstradiation from the first prism via the plurality of lenses of the lensassembly and reflect the first radiation. The optical system may furtherinclude a second prism configured to receive the first radiationreflected from the mirror via the plurality of lenses of the lensassembly and direct the first radiation on an optical path toward theimage plane. The first set of lenses may be configured to pass the firstradiation to the first prism. The second prism may be configured to passthe first radiation to the second set of lenses.

In one or more aspects, the actuator system may be configured to adjustthe second set of lenses to apply a first magnification compensationvalue along the first direction to the magnification and to apply asecond magnification compensation value along the second direction tothe magnification. The first magnification compensation value may bedifferent from the second magnification compensation value. The actuatorsystem may be configured to move at least one lens of the first set oflenses from a first position to a second position and/or at least onelens of the second set of lenses from a third position to a fourthposition to adjust the magnification. In some cases, the second set oflenses is a single lens, where the actuator system may be configured tobend and/or rotate the single lens to adjust the magnification.

In one or more embodiments, the optical system is a lithography system.The object may include a pattern of a mask. The image plane may includea wafer. The image may include a projection of the object on the wafer.The optical system may further include a magnification controllerconfigured to generate one or more control signals associated with anadjustment to the magnification based at least on a position of the maskrelative to a position of the wafer. The actuator system may beconfigured to receive the one or more control signals and causeadjustment of the magnification in response to the one or more controlsignals. The optical system may further include a wafer positioningcontroller configured to adjust the position of the wafer relative tothe position of the mask to shift a position of the image on the wafer.In some aspects, the lens system may be configured to project arespective portion of the pattern onto a respective portion of thewafer. The actuator system may be further configured to adjust the tiltof the beam steering lens in response to the one or more controlsignals, with each portion of the wafer being associated with arespective tilt of the beam steering lens.

In one or more embodiments, a method includes receiving first radiationassociated with an object. The method further includes directing thefirst radiation through at least a first set of lenses to obtainselectively magnified first radiation, where, during the directing thefirst radiation, selectively adjusting the first set of lenses to adjusta magnification associated with an image of the object symmetricallyalong a first direction and a second direction. The method furtherincludes directing, based at least on a tilt of a beam steering lens,the selectively magnified first radiation to provide second radiationtoward an image plane. In some aspects, the first set of lenses mayinclude a plurality of lenses, where selectively adjusting the first setof lenses may include adjusting a distance between at least two of theplurality of lenses. The first direction may be orthogonal to the seconddirection. In some cases, the image plane may be parallel to an objectplane. In other cases, the image plane is not parallel to the objectplane.

In one or more aspects, the directing the first radiation may includedirecting the first radiation through at least the first set of lensesand a second set of lenses to obtain the selectively magnified firstradiation, where, during the directing the first radiation, selectivelyadjusting the second set of lenses to adjust the magnification along thefirst direction or the second direction. The selectively adjusting thesecond set of lenses may include selectively adjusting the second set oflenses to apply a first magnification compensation value along the firstdirection to the magnification and to apply a second magnificationcompensation value different from the first magnification compensationvalue along the second direction to the magnification.

In some embodiments, the method is utilized for a lithography system.The object may include a pattern of a mask. The image plane may includea wafer. The image may include a projection of the object on the wafer.The directing the selectively magnified first radiation may includeprojecting each portion of the pattern onto a respective portion of thewafer. In some aspects, the method may further include generating one ormore control signals associated with an adjustment to the magnificationbased at least on a position of the mask relative to a position of thewafer, where the selectively adjusting the first set of lenses is basedon the one or more control signals. The method may further includeadjusting a tilt of a beam steering lens in response to the one or morecontrol signals, where each portion of the wafer is associated with arespective tilt of the beam steering lens.

In one or more embodiments, an optical system includes a lens systemconfigured to receive first radiation associated with an object anddirect second radiation associated with an image of the object toward animage plane. The lens system includes a first set of lenses configuredto receive and selectively magnify the first radiation. The lens systemalso includes a second set of lenses configured to receive andselectively magnify the first radiation. The lens system also includesan actuator system configured to selectively adjust the first set oflenses to adjust a magnification associated with the image symmetricallyalong a first direction and a second direction. The actuator system isalso configured to selectively adjust the second set of lenses to adjustthe magnification along at least one of the first direction or thesecond direction. In one or more aspects, the lens system may furtherinclude a beam steering lens configured to direct the first radiationbased at least on a tilt of the beam steering lens to provide the secondradiation. The tilt of the beam steering lens may be adjustable by theactuator system.

In some embodiments, the optical system further includes a lens assemblyincluding a plurality of lenses. The optical system further includes afirst prism configured to pass the first radiation to the lens assembly.The optical system further includes a mirror configured to receive thefirst radiation from the first prism via the plurality of lenses of thelens assembly and reflect the first radiation. The optical systemfurther includes a second prism configured to receive the firstradiation reflected from the mirror via the plurality of lenses of thelens assembly and direct the first radiation on an optical path towardthe image plane. The first set of lenses may be configured to pass thefirst radiation to the first prism, and the second prism may beconfigured to pass the first radiation to the second set of lenses.

In some aspects, the actuator system may be configured to adjust thesecond set of lenses to apply a first magnification compensation valuealong the first direction to the magnification and to apply a secondmagnification compensation value along the second direction to themagnification. The first magnification compensation value may bedifferent from the second magnification compensation value. In somecases, the first direction may be orthogonal to the second direction. Insome implementations, the actuator system may be configured to move atleast one lens of the first set of lenses from a first position to asecond position and/or at least one lens of the second set of lensesfrom a third position to a fourth position to adjust the magnification.

In some embodiments, the optical system may be a lithography system. Theobject may include a pattern of a mask. The image plane may include awafer. The image may include a projection of the object on the wafer.The optical system may include a beam steering lens configured toprovide the second radiation based at least on a tilt of the beamsteering lens. The lens system may be configured to project a respectiveportion of the pattern onto a respective portion of the wafer. Theactuator system may be further configured to adjust a tilt of the beamsteering lens in response to one or more control signals. Each portionof the wafer may be associated with a respective tilt of the beamsteering lens.

In one or more embodiments, a method includes receiving radiationassociated with an object. The method includes directing the radiationtoward an image plane through at least a first set of lenses and asecond set of lenses. The method includes, during the directing,selectively adjusting the first set of lenses to adjust a magnificationassociated with an image of the object symmetrically along a firstdirection and a second direction; and selectively adjusting the secondset of lenses to adjust the magnification along the first direction orsecond direction.

In some embodiments, such as for lithography systems, the object includea pattern of a mask, the image plane may include a wafer, the image mayinclude a projection of the object on the wafer, and the directing theradiation includes projecting each portion of the pattern onto arespective portion of the wafer. The method may further includegenerating one or more control signals based at least on a position ofthe mask relative to a position of the wafer. The method may furtherinclude adjusting a tilt of a beam steering lens in response to the oneor more control signals. Each portion of the wafer may be associatedwith a respective tilt of the beam steering lens.

In one or more embodiments, a method includes providing a first set oflenses of a lens system and a second set of lenses of the lens system.The method further includes receiving, by the lens system, firstradiation associated with an object. The method further includesdirecting the first radiation through the first set of lenses to magnifythe first radiation symmetrically along a first direction and a seconddirection orthogonal to the first direction. The method further includesdirecting the first radiation through the second set of lenses tomagnify the first radiation along the first direction or the seconddirection. The method further includes directing second radiationassociated with an image of the object toward an image plane, where thesecond radiation is based on the first radiation having passed the firstand second set of lenses.

The scope of the disclosure is defined by the claims, which areincorporated into this section by reference. A more completeunderstanding of embodiments of the disclosure will be afforded to thoseskilled in the art, as well as a realization of additional advantagesthereof, by a consideration of the following detailed description of oneor more embodiments. Reference will be made to the appended sheets ofdrawings that will first be described briefly.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 illustrates an optical system in accordance with one or moreembodiments of the present disclosure.

FIGS. 2A and 2B illustrate a symmetric magnification lens set, anasymmetric magnification lens set, and an associated mounting system andactuator system in accordance with one or more embodiments of thepresent disclosure.

FIGS. 3A through 3C illustrate examples of relative positioning oflenses of a symmetric magnification lens set in accordance with one ormore embodiments of the present disclosure.

FIG. 4A illustrates an example cross-sectional view of a symmetricmagnification lens set to in accordance with one or more embodiments ofthe present disclosure.

FIG. 4B illustrates an example cross-sectional view of an asymmetricmagnification lens set in accordance with one or more embodiments of thepresent disclosure.

FIG. 5 illustrates a lens duo of an optical system in accordance withone or more embodiments of the present disclosure.

FIG. 6 illustrates an asymmetric magnification lens in accordance withone or more embodiments of the present disclosure.

FIG. 7 illustrates a beam steering lens of an optical system inaccordance with one or more embodiments of the present disclosure.

FIG. 8 illustrates a beam steering lens and associated components inaccordance with one or more embodiments of the present disclosure.

FIG. 9 illustrates a lithography system in accordance with one or moreembodiments of the present disclosure.

FIG. 10 illustrates a scanning lithography machine or portion thereof inaccordance with one or more embodiments of the present disclosure.

FIGS. 11A and 11B illustrate examples of exposure fields for a scanninglithography machine.

FIG. 12 illustrates actual and desired die size and location for variousdie on a wafer.

FIGS. 13A and 13B provide enlarged views of die of FIG. 12.

FIGS. 14A through 14C illustrate tilting of a beam steering lens of anoptical system as a wafer is moved, in accordance with one or moreembodiments of the present disclosure.

FIGS. 15A through 15D illustrate a position of a scanner exposure fieldof view and associated wafer position shifting in accordance with one ormore embodiments of the present disclosure.

Embodiments of the present disclosure and their advantages are bestunderstood by referring to the detailed description that follows. Itshould be appreciated that like reference numerals are used to identifylike elements illustrated in one or more of the figures.

DETAILED DESCRIPTION

The detailed description set forth below is intended as a description ofvarious configurations of the subject technology and is not intended torepresent the only configurations in which the subject technology can bepracticed. The appended drawings are incorporated herein and constitutea part of the detailed description. The detailed description includesspecific details for the purpose of providing a thorough understandingof the subject technology. However, it will be clear and apparent tothose skilled in the art that the subject technology is not limited tothe specific details set forth herein and may be practiced using one ormore embodiments. In one or more instances, structures and componentsare shown in block diagram form in order to avoid obscuring the conceptsof the subject technology. One or more embodiments of the subjectdisclosure are illustrated by and/or described in connection with one ormore figures and are set forth in the claims.

Various techniques are provided to facilitate magnification compensationand beam steering in optical systems. The magnification compensation maybe utilized to account for magnification error, such as due to imperfectplacement of die on a wafer, wafer and/or mask expansion, and/or othersituations. In some embodiments, an optical system may include sets oflenses to provide magnification compensation (e.g., also referred to asmagnification correction or magnification adjustment). The sets oflenses utilized for magnification compensation may collectively bereferred to as magnification compensation lenses. The magnificationcompensation may be used to adjust (e.g., change, correct, compensate) anominal magnification of the optical system. In this regard, the nominalmagnification of the optical system may refer to a magnification of theoptical system without any magnification compensation provided by themagnification compensation lenses. In an aspect, the magnificationcompensation provided by the magnification compensation lenses may bereferred to simply as magnification, since magnification compensationlenses are effectively providing magnification to the object. As usedherein, a magnification provided by the magnification compensationlenses may be a positive magnification (e.g., image is made largerrelative to a case without the provided magnification), negativemagnification (e.g., image is made smaller relative to a case withoutthe provided magnification), or zero magnification (e.g., magnificationcompensation lenses do not magnify or demagnify). In an aspect,magnification may refer to a ratio of an image size at an image plane(e.g., also referred to as a subject plane) to an object size at anobject plane.

A first set of lenses may provide the same magnification compensationalong both an x-direction and a y-direction that is orthogonal to thex-direction. Such magnification compensation may be referred to assymmetric magnification compensation or rotation symmetric magnificationcompensation. The first set of lenses may be referred to as, or may beimplemented by, a symmetric magnification lens set. The symmetricmagnification lens set may include one or more symmetric lenses, such asone or more spherical lenses. A second set of lenses may providedifferent magnification compensation along the x-direction and/ory-direction. Such magnification compensation may be referred to as asingle axis magnification compensation or asymmetric magnificationcompensation. The second set of lenses may be referred to as anasymmetric magnification lens set. The asymmetric magnification lens setmay include one or more asymmetric lenses, such as one or morecylindrical lenses. Although the optical system described in variousembodiments of the present disclosure include one set of lenses forsymmetric magnification compensation and another set of lenses forasymmetric magnification compensation, the optical system may includefewer sets of lenses, additional sets of lenses, and/or differentcombination of sets of lenses to provide symmetric magnificationcompensation and/or asymmetric magnification compensation in otherembodiments. For example, in one embodiment, the optical system mayinclude a single set of lenses for symmetric magnification compensation(e.g., without a set of lenses for asymmetric magnificationcompensation).

Each set of lenses may include one or more lenses (e.g., one or moreconvex lenses and/or one or more concave lenses). In an aspect, thefirst set of lenses may include three lenses (e.g., also referred to asa lens trio). As an example, the three lenses may include twoplano-concave lenses and one biconvex lens. As another example, thethree lenses may include two plano-convex lenses and one biconcave lens.

The optical system may include an actuator system to facilitateadjustment of the magnification compensation provided by themagnification compensation lenses. As an example, in a case that a setof lenses includes two or more lenses, the magnification compensationprovided by this set of lenses may be adjusted by adjusting a size of agap (e.g., an air gap) between at least two of the lenses in the set. Inthis regard, the actuator system may move one or more of the lenses inthe set to adjust the size of the gap. As another example, in a casethat a set of lenses includes a single lens, the magnificationcompensation provided by the single lens may be adjusted by bending(e.g., deforming) the single lens, such as by applying force using theactuator system.

In one or more embodiments, the optical system may include one or morebeam steering elements to direct a beam to an image plane. A beamsteering element may be, or may be referred to as, a beam steering lens,beam steering window, tilting lens, tilting window, and/or variantsthereof. The beam steering element(s) may receive a beam that haspropagated through the first and second sets of lenses.

Using various embodiments, magnification of an optical system, such as atelecentric optical system, may be controlled. In some embodiments, theoptical systems may be, may include, or may be a part of, asemiconductor lithography system, such as a Wynn-Dyson 1:1 (e.g., unitmagnification) scanning projection system and/or other photolithographicimage systems, and/or generally any projection lens system forprojecting an image of an object at an object plane onto an image plane.In some aspects, for projection lens systems that are telecentric inobject and image, magnification cannot be changed by changing object orimage distances. In some cases, large radius convex and concave lensesmay be employed in projection lens object telecentric space or imagetelecentric space to provide magnification compensation. The use ofmagnification compensation lenses in a projection lens system allows themagnification provided by the optical system to be adjusted. In somecases, the addition of magnification compensation lenses of largerradius into a projection lens system causes smaller impact to imageperformance (e.g., relative to addition of smaller magnificationcompensation lenses). Magnification compensation and beam steering maybe performed quickly to maintain throughput while reducing magnificationerror. Furthermore, such techniques allow for asymmetric magnificationcompensation, in which different magnification compensation is providedfor different directions.

Turning now to the figures, FIG. 1 illustrates an optical system 100 inaccordance with one or more embodiments of the present disclosure. Notall of the depicted components may be required, however, and one or moreembodiments may include additional components not shown in FIG. 1.Variations in the arrangement and type of the components may be madewithout departing from the spirit or scope of the claims as set forthherein. Additional, fewer, and/or different components may be provided.In an embodiment, the optical system 100 may be utilized to provideoptical asymmetric magnification with beam steering.

Various optical components of the optical system 100 reflect and/orrefract radiation incident on or propagating through the opticalcomponents. In some aspects, the radiation is electromagnetic (EM)radiation. EM radiation may generally refer to any radiation in the EMspectrum and may be referred to as an EM beam of radiation, EM beam,light, beam, or variant thereof (e.g., EM beam of light). The term lightmay include visible light, infrared light, ultraviolet (UV) light, orgenerally any portion of the EM spectrum. In some cases,light-transmissive surfaces of various components of the optical system100 may be coated with material to increase light-transmissiontherethrough. Alternatively and/or in addition, reflective surfaces ofvarious components of the optical system 100 may be coated to increasereflectivity.

In one embodiment, such as shown in FIG. 1, an object plane 105 isparallel to and spaced from an image plane 110 along a z-direction(e.g., vertical direction in FIG. 1). An example distance between theobject plane 105 and the image plane 110 is around 8.58 inches. Theobject plane 105 and image plane 110 are disposed on opposite sides ofthe optical system 100. A radiation source (not shown in FIG. 1) mayprovide a beam 115 (e.g., EM radiation) through the object plane 105 andto the optical system 100. For example, the radiation source may be alight source, such as a UV light source. The beam 115 may propagatethrough various components of the optical system 100 and be output as abeam 120 to the image plane 110. In this manner, an image of an objectat the object plane 105 may be projected onto the image plane 110. Inother embodiments, the object and image plane are at a defined angle toone another (e.g., the object and image plane are not parallel to oneanother).

In an embodiment, for example, when the optical system 100 is providedas part of a lithography system (e.g., a semiconductor lithographysystem), a reticle, mask, or generally any structure that has amicroelectronics pattern defined thereon (e.g., on a plate/film ofmaterial) may be provided as an object at the object plane 105 to beprojected onto the image plane 110. A wafer on which structures are tobe fabricated or manufactured may be provided at the image plane 110 toreceive the projection of the microelectronics pattern. In this regard,the beam 115 propagates through the object (e.g., reticle, mask, etc.)at the object plane 105 and is directed by the optical system 100 to theimage plane 110. In some cases, the optical system 100 may applymagnification (e.g., positive or negative magnification) to the beam115. In an aspect, magnification may refer to a ratio of an image sizeat the image plane 110 to an object size at the object plane 105.

In some embodiments, the optical system 100 includes a symmetricmagnification lens set 125, an asymmetric magnification lens set 130, abeam steering lens 135, prisms 140 and 145, a lens assembly 150, and amirror 155. In some cases, the dashed box in FIG. 1 may represent ahousing of the optical system 100. For example, the housing may includea window and/or material that allows the beam 115 to pass into (e.g.,couple into) the optical system 100. In some aspects, the asymmetricmagnification lens set 130 is optional as described further herein.

The lens assembly 150 includes lenses 160, 165, 170, and 175. The lens160, 165, 170, and 175 may be a plano-convex lens, concavo-convex lens,convexo-concave lens, and meniscus lens, respectively. In an aspect, themirror 155 and lenses 160, 165, 170, and 175 are positioned (e.g.,mounted) along an optical axis of the optical system 100. An opticalaxis of the optical system 100 may refer to an axis through which a beamcan traverse without being refracted. In an aspect, the lenses 160, 165,170, and 175 are made of material and/or positioned to collectivelycorrect for chromatic aberrations, field aberrations, and/orastigmatism. The lenses 160, 165, 170, and 175 may be made of the sameor different glass types.

The lens 160 has a plane surface facing away from the mirror 155 and aconvex surface facing the mirror 155. The convex surface of the lens 160may face a concave surface of the lens 165. In some cases, the convexsurface of the lens 160 may be nested into the concave surface of thelens 165. For example, the lenses 160 and 165 may be cemented togetherto form a doublet. The lens 165 has a convex surface facing the mirror155. A curvature of the convex surface of the lens 165 may be less thanthat of the concave surface of the lens 165 and less than that of theconvex surface of the lens 160.

The lens 170 has a convex surface facing away from the mirror 155 andtoward the lens 160 and a concave surface facing the mirror 155. Thelens 175 has a convex surface facing the mirror 155 and a concavesurface facing away from the mirror 155 and toward the lens 160. In somecases, the curvatures of the surfaces of the lens 175 are less thanthose of the lens 165 and those of the lens 170.

The mirror 155 has a concave surface 180 centered on an optical axis ofthe optical system 100 and facing the lens 160. The concave surface 180may be spherical or slightly aspherical (e.g., to also referred to assubstantially spherical). The concave surface 180 may be slightlyspherical (e.g., slightly ellipsoidal) to help correct high-orderchromatic aberrations for a large field. In an aspect, the shape of theconcave surface 180 and the lenses 160, 165, 170, and 175 of the lensassembly 150 and positioning/arrangement thereof may facilitatecorrection of chromatic aberrations. It is noted that the foregoingprovides example characteristics of the lenses 160, 165, 170, and 175.Other combinations of lenses and/or lens characteristics may beutilized. In an embodiment, the lenses 160, 165, 170, and 175 can beeither spherical or aspherical. Other embodiments of the Dyson lens areknown to those skilled in the art and can be used with the definedmagnification and beam steering described in the present disclosure.

The prism 140 (e.g., also referred to as a roof prism) and the prism 145(e.g., also referred to as a fold prism) are between the object plane105 and the image plane 110. An example distance between the objectplane and a top surface of the prism 140 is around 1.41 inches. In somecases, such as shown in FIG. 1, the prisms 140 and 145 are mountedadjacent to each other and to the lens 160. In this regard, the prisms140 and 145 are adjacent to a side of the lens 160 that is farther fromthe mirror 155. The prisms 140 and 145 each have a planar face that isadjacent to a planar face of the lens 160. This planar face of theprisms 140 and 145 lies in a plane perpendicular to the object plane105, image plane 110, and an optical axis of the lens assembly 150 andmirror 155.

The prism 140 has an apex edge 142 that extends toward the object plane105 at a 45° angle to the object plane 105 and 45° angle to the planarsurface of the lens 160. The prism 140 has roof surfaces that are planarand extend to the apex edge 142. The roof surfaces may be at a 90° angleof each other. The prism 145 has a planar face parallel to and facingthe object plane 105. The prism 145 has a face 147 lying at a 45° angleto the object plane 105 and image plane 110. The face 147 isperpendicular to a plane that contains the apex edge 142 of the prism140 and to the object plane 105 and image plane 110. The face 147 andthe apex edge 142 of the prism 140 are convergent, relative to eachother, in a direction toward the mirror 155. The prisms 140 and 145 arecontiguous to each other generally in a plane that is around halfwaybetween and parallel to the object plane 105 and image plane 110. Insome cases, such as shown in FIG. 1, the prisms 140 and 145 have a flatsurface that are contiguous to each other at this halfway point.

The prisms 140 and 145 and the lenses 160, 165, 170, and 175 areappropriately sized (e.g., sufficiently large) to receive and pass aparticular field size and shape to be projected from the object plane105 to the image plane 110. The symmetric magnification lens set 125 andasymmetric magnification lens set 130 may be utilized to provide aparticular field size and shape. In FIG. 1, the symmetric magnificationlens set 125 is positioned between the object plane 105 and the prism140, and the asymmetric magnification lens set 130 is positioned betweenthe prism 145 and the image plane 110. The symmetric magnification lensset 125 may magnify the beam 115 received from the object plane 105. Theasymmetric magnification lens set 130 may magnify a beam passed throughthe prism 145 to provide the beam 120 to the image plane 110. In aspectswhere the asymmetric magnification lens set 130 is not provided in theoptical system 100, the prism 145 may provide the beam 120 to the imageplane 110. For example, in an embodiment without the asymmetricmagnification lens set 130, remaining components of FIG. 1 may remain asshown in FIG. 1, except with a surface of the prism 145 facing a surfaceof the beam steering lens 135 and the prism 145 providing the beam 120to the image plane 110 via the beam steering lens 135.

The symmetric magnification lens set 125 provides symmetricmagnification compensation along the x- and y-directions. The symmetricmagnification lens set 125 includes lenses 125A-C. The lenses 125A-C maybe, or may collectively provide, one or more spherical lenses. In oneexample, the lenses 125A, 125B, and 125C may be a plano-concave lens,biconvex lens, and concave-plano lens, respectively. In another example,the lenses 125A, 125B, and 125C may be a plano-convex lens, biconcavelens, and convex-plano lens. In an aspect, at least one of the lenses125A-C may be moveable (e.g., via translational motion) by an actuatorsystem (not shown in FIG. 1) associated with the optical system 100 toadjust the symmetric magnification compensation provided by thesymmetric magnification lens set 125. For example, the actuator systemmay be provided as part of or otherwise coupled to the optical system100. In some cases, one or two of the lenses 125A-C are movable whereasthe remaining of the lenses 125A-C are intended to remain fixed inposition. In a further embodiment, all the lenses 125A-C are moveable.

The asymmetric magnification lens set 130 provides magnificationcompensation adjustment along one or both of the x- or y-direction. Theasymmetric magnification lens set 130 includes lenses 130A-C. The lenses130A-C may be, or may collectively provide, one or more cylindricallenses. In one example, the lenses 130A, 130B, and 130C may be aplano-convex lens, concave-concave lens, and a convex-plano lens. Inanother example, the lenses 130A-C may be a plano-concave lens, biconvexlens, and concave-plano lens, respectively. A thickest portion of thelenses 130A-C may be around 2 mm to 10 mm. In one example, the lenses130A-C may be made using circular, square, or rectangular glass. In somecases, a rectangular external shape may be easier for production andalignment. In an aspect, at least one of the lenses 130A-C may bemoveable (e.g., via translational motion) by the actuator systemassociated with the optical system 100 to adjust the asymmetricmagnification compensation provided by the asymmetric magnification lensset 130. In some cases, one or two of the lenses 130A-C are movablewhereas the remaining of the lenses 130A-C are intended to remain fixedin position. In a further embodiment, all the lenses 130A-C aremoveable.

In an aspect, the asymmetric magnification compensation range providedby the asymmetric magnification lens set 130 may be smaller (e.g., maybe designed to be smaller) than the symmetric magnification compensationrange provided by the symmetric magnification lens set 125, since largerasymmetric magnification compensation may affect system astigmatism. Asan example, the symmetric magnification lens set 125 may be utilized toprovide a symmetric magnification compensation range of −250 parts permillion (ppm) to +250 ppm along both the x- and y-directions, whereasthe asymmetric magnification lens set 130 may be utilized to providemagnification compensation range of −50 ppm to +50 ppm along one or bothof the x- or y-directions. In an aspect, a positive magnificationcompensation provides an increase in magnification (e.g., relative to acase without the magnification compensation lenses), a negativemagnification compensation provides a decrease in magnification, andzero magnification compensation maintains the magnification. In thisexample, the optical system 100 may provide a compensation range ofabout ±250 ppm symmetric compensation and single-axis compensation rangeof about ±50 ppm.

In an aspect, the symmetric magnification lens set 125 may be, or may beconsidered to be, two pairs of lenses. For example, a size of a gap(e.g., an air gap) between a first pair of lenses may providemagnification compensation range of 0 to +250 ppm, and a size of a gapbetween a second pair of lenses may provide magnification compensationrange of −250 ppm to 0. In this regard, the first pair of lenses mayinclude the lenses 125A and 125B, and the second pair of lenses mayinclude the lenses 125B and 125C.

Optionally, a beam steering lens 135 may receive an output of theasymmetric magnification lens set 130 and direct the beam 120 to theimage plane 110. In some cases, the beam steering lens 135 may have anadjustable tilt to direct the beam 120 along the x and/or y-directions(e.g., relative to a case without the beam steering lens 135). Inaspects where the asymmetric magnification lens set 130 is not providedin the optical system 100, the prism 145 may provide the beam 120 to thebeam steering lens 135 and the beam steering lens 135 may direct thebeam 120 to the image plane 110.

An optical path of the optical system 100 is a path that the beam 115provided from the object plane 105 takes in traversing through theoptical system 100 to be provided as the output beam 120 to be directedonto the image plane 110. It is noted that an intensity of the beam 115may be attenuated, such as by absorption and/or scattering losses, asthe beam 115 traverses through the optical path, through variouscomponents (e.g., lenses, mirrors) along the optical path, and/orimpinges on mirror surfaces.

In traversing through an optical path of the optical system 100, thebeam 115 passes an object at the object plane 105 and enters the opticalsystem 100. After entering the optical system 100, the beam 115 passesthrough the symmetric magnification lens set 125. The symmetricmagnification lens set 125 may apply symmetric magnificationcompensation to the beam 115. A resulting beam exits the symmetricmagnification lens set 125, passes through the prism 140, and isreflected by the prism 140, such as by the apex edge 142, in differentdirections. The beam reflected by the prism 140 passes through, inorder, the lenses 160, 165, 170, and 175 and strikes different portionsof the concave surface 180 of the mirror 155. The concave surface 180 ofthe mirror 155 reflects the incident beam. The beam reflected by theconcave surface 180 passes through, in order, the lenses 175, 170, 165,and 160 and to the prism 145, following which the prism 145 directs thebeam toward the asymmetric magnification lens set 130. The asymmetricmagnification lens set 130 may apply asymmetric magnificationcompensation to the beam. A resulting beam may be provided to the beamsteering lens 135 to be directed by the beam steering lens 135 to theimage plane 110. An output of the beam steering lens 135 is the beam120, which may be considered an output beam of the optical system 100.

It is noted that FIG. 1 illustrates an example combination of the prisms140 and 145, lenses 160, 165, 170, and 175 of the lens assembly 150, andmirror 155 and arrangement thereof (e.g., relative to the object plane105 and image plane 110). In some cases, fewer, more, and/or differentcomponents may be employed in the optical system 100. As one example,although the symmetric magnification lens set 125 and the asymmetricmagnification lens set 130 are each depicted as having three lenses, thesymmetric magnification lens set 125 and the asymmetric magnificationlens set 130 may each have a different number of lenses than the threelenses depicted in FIG. 1, such as one lens, two lens, or more thanthree lenses. The symmetric magnification lens set 125 may have adifferent number of lenses than the asymmetric magnification lens set130. As another example, in some cases, the beam steering lens 135 isnot employed in the optical system 100. As another example, one or moreof the lenses 160, 165, 170, and 175 of the lens assembly 150 is notemployed in the optical system 100.

Other combinations of components and/or arrangements thereof may beemployed in an optical system. As one variation, the positions of theprisms 140 and 145 can be reversed without affecting operation of theprisms 140 and 145. As another variation, the symmetric magnificationlens set 125 and/or asymmetric magnification lens set 130 may beprovided at different locations than that shown in FIG. 1. For example,in one embodiment, the symmetric magnification lens set 125 may beplaced between the prism 140 and the lens 160. In another example, thelens sets 125 and 130 may be placed between the lens 160 and either orboth the prisms 140 and 145. In another example, the lens sets 125 and130 may be reversed in position from that shown in FIG. 1, or generallyreversed in position such that the lens set 130 is placed at an earlierpoint in the optical path than the lens set 125. In one variation ofthis example, the asymmetric magnification lens set 130 may be placedabove the prism 140 and the symmetric magnification lens set 125 may beplaced below the prism 145. In other words, the asymmetric magnificationlens set 130 is at an earlier point in the optical path than the prism140, and the symmetric magnification lens set 125 is at a later point inthe optical path than the prism 145. In another configuration, the lensset 125 and 130 can be combined into a single set of lenses and placedin any of the previously defined locations. Various combinations ofthese examples and/or other arrangements may be utilized in placing thelens sets 125 and/or 130 relative to the prisms 140 and 145 and lens160. Additional examples of combinations of components and/orarrangements thereof are provided in U.S. Pat. No. 5,559,629, which isincorporated herein by reference in its entirety.

Although the optical system 100 of FIG. 1 illustrates an example inwhich the object plane 105 is parallel to the image plane 110, inanother embodiment (not shown), the object plane 105 and image plane 110are not parallel to each other. In such an embodiment, the face of theprism 140 closest to the object plane 105 is parallel to the objectplane 105 and the face of the prism 145 closest to the image plane 110is parallel to the image plane 110. The faces of the prism 140 and 145closest to the lens 160 are parallel. In such an embodiment, forexample, the prisms 140 and 145 can both be internally reflecting foldprisms.

FIGS. 2A and 2B illustrate views of the symmetric magnification lens set125 and asymmetric magnification lens set 130 of the optical system 100and an associated mounting system and actuator system in accordance withone or more embodiments of the present disclosure. Not all of thedepicted components may be required, however, and one or moreembodiments may include additional components not shown in FIGS. 2A and2B. Variations in the arrangement and type of the components may be madewithout departing from the spirit or scope of the claims as set forthherein. Additional, fewer, and/or different components may be provided.For explanatory purposes, other components of the optical system 100,such as the prisms 140 and 145 and lenses 160, 165, 170, and 175, arenot shown in FIGS. 2A and 2B. As shown in FIGS. 2A and 2B, the opticalsystem 100 may include a housing 202 (e.g., also referred to as anenclosure) within which the various components shown in FIG. 1 andassociated mounting system and actuator system are disposed.

The mounting system may include structural features/components (e.g.,screws, adhesive, clamps, receiving interfaces, etc.) that help support(e.g., hold in place) the lens sets 125 and 130 (and possibly othercomponents of the optical system 100). The actuator system may includean actuator 205, an actuator 210, an actuator controller 215, a feedbackdevice 220, and a feedback device 225. The actuator 205 may beconfigured to move one or more lenses of the symmetric magnificationlens set 125. For example, one, two, or all three lenses of thesymmetric lens set 125 may be movable by the actuator 205, whileremaining lenses (if any) of the symmetric lens set 125 remain fixed inposition. Similarly, the actuator 210 may be configured to move one ormore lenses of the asymmetric lens set 130. The actuator controller 215may receive information and generate control signals for the actuators205 and 210 based on the received information. The feedback devices 220and 225 may each be, may each include, or may each be a part of, anencoder; capacitive, inductive or laser sensor; strain gauge; and/orgenerally any device that can be used to verify a position of the lenses125A-C and 130A-C, respectively, before, during, and after motion. Inthis regard, the actuator controller 215 and feedback devices 220 and225 may operate in tandem (e.g., exchange appropriate information) tohelp ensure the lenses 125A-C and 130A-C are at appropriate positionsbefore, during, and after motion of one or more of the lenses 125A-C andone or more of the lenses 130A-C.

In an embodiment, the actuator controller 215 may receive informationassociated with a relative positioning of a mask and a wafer. In alithography system, images of the mask and wafer may be captured bycamera systems to determine an expected projection of the mask (e.g.,pattern of the mask) onto the wafer. The expected projection may be usedto determine magnification compensation and/or beam steering needed toadjust from the expected projection to a desired projection. Forexample, if the image of the wafer targets taken at one or morelocations on the wafer is further out from the center of the wafer thanthe mask targets, then the wafer is determined to have positivemagnification and appropriately positive magnification and steeringcould be applied. If the image of the wafer targets is closer to thecenter of the wafer than the mask targets, then the wafer is determinedto have negative magnification and appropriately negative magnificationand steering could be applied. It should be noted that the above exampleis defined as a case where the mask has no magnification bias. In thecase where the mask has a magnification bias, then the appropriatecalculations can be applied to provide the desired magnification. Ingeneral, it is desirable that the printed mask image matches themagnification of the exiting wafer image (known as zero magnification orzero mag) such that newly printed features properly overlay ontopreviously printed features across all elements of a wafer. In thisregard, using various embodiments, it is possible to print zeromagnification, positive magnification, or negative magnification asdesired. In addition, offsets in position of wafer targets relative tomask targets may be corrected using beam steering.

In some aspects, multiple points are inspected on the wafer relative tothe mask to determine the appropriate alignment. In some cases, forsymmetric magnification compensation, a minimum of two points are neededto determine if symmetric magnification compensation should be utilized,and for asymmetric magnification compensation, at least three points maybe needed, and preferably four points are inspected, to determine ifasymmetric magnification compensation should be utilized. However, morepoints on the wafer can be inspected to give an overall better alignmentand magnification performance.

An additional use of beam steering or micro wafer positioning can beused to compensate for small translational and/or rotational differencesbetween the mask and wafer that are identified during the alignmentroutine. For example, if the wafer is translated relative to the mask,the wafer can be repositioned to be directly under the mask, or the beamsteering can be utilized to compensate for the offset. Suchrepositioning and/or beam steering may be applied to rotationaldifferences as well. It can also be applied in cases where there is adifferent correction required in x-direction versus the y-direction forthe alignment.

In some cases, the control signals may indicate magnificationcompensation to be provided by the lens set 125 and/or 130. In thesecases, the actuator 205 and 210 may determine (e.g., using a processor)a distance to move one or more of the moveable lens or lenses toeffectuate the magnification compensation indicated in the controlsignals and move the appropriate lens or lenses by the determineddistance. In other cases, alternatively and/or in combination, thecontrol signals may directly indicate to the actuators 205 and/or 210 adistance to move one or more of the moveable lens or lenses of theirrespective lens set.

As discussed previously, a change in magnification of the imageprojected onto the image plane 110 may be effectuated by adjusting oneor both of the symmetric magnification lens set 125 and asymmetricmagnification lens set 130. FIGS. 3A through 3C illustrate examples ofrelative positioning of the lenses 125A-C of the symmetric magnificationlens set 125 in accordance with one or more embodiments of the presentdisclosure. In FIGS. 3A through 3C, the lenses 125A-B remain fixed inposition while the lens 125C is moveable along the direction ofpropagation of light 305 (e.g., the z-direction).

A dashed line 310 in FIGS. 3A-3C depicts an optical path for a portionof the light 305 that passes through an optical axis of the symmetricmagnification lens set 125. The lenses 125A-C of the symmetricmagnification lens set 125 are positioned such that their respectiveoptical axis overlap. A portion of the light 305 that passes through anoptical axis of the symmetric magnification lens set 125 is notrefracted (e.g., bent) by the lenses 125A-C. A dashed line 315 in FIGS.3A-3C is parallel to and displaced by a distance r from an optical axisalong the x-direction. A solid line 320, 325, and 330 in FIG. 3A, 3B,and 3C, respectively, is an optical path of a portion of the light 305that enters the lens 125A, from the z-direction, at the distance r fromthe line 310.

To adjust the magnification compensation provided by the symmetricmagnification lens set 125, a distance between a topmost surface of thelens 125A and a bottommost surface of the lens 125C (denoted as D_(A),D_(B), and D_(C) in FIGS. 3A, 3B, and 3C, respectively) is adjusted bymoving the lens 125C (e.g., by an actuator) along the z-direction whilethe lenses 125A and 125B are fixed in position. As an example, in FIGS.3A-3C, D_(A)<D_(B)<D_(C). In other cases, alternatively and/or inaddition, the lenses 125A and/or 125B may be moveable to adjust thedistance between the topmost surface of the lens 125A and the bottommostsurface of the lens 125C. In some cases, a fewer number of moveablelenses may be associated with a reduced number of actuators and/orcomplexity.

In FIGS. 3A-3C, since only the lens 125C is movable in this example, thedifferent distances D_(A), D_(B), and D_(C) are attributed to adifferent gap size (e.g., air gap size) between the lenses 125B and125C. For beams with optical paths away from the optical axis that isdenoted by the line 310, the lenses 125A and 125B refracts the beams. Inrelation to the line 315, the optical path of the beams (shown by thesolid lines 320, 325, and 330) deviate from each other during theportion of the optical path after exiting the lens 125B, due to thedifferent gaps between the lenses 125B and 125C to be traversed by thebeams. In FIG. 3A, a beam exits the lens 125B and converges toward theline 315, but does not reach the line 315. A distance between the line310 and the line 320 at an output of the lens 125C is denoted by r_(A).In this regard, the gap between the lenses 125B and 125C results inr<r_(A), which indicates that the symmetric magnification lens set 125increases magnification. An increase in magnification may be referred toas a positive magnification compensation.

In FIG. 3B, a beam exits the lens 125B, converges toward the line 315,and overlaps the line 315. A distance between the line 310 and the line325 at an output of the lens 125C is denoted by r_(B). In this regard,the gap between the lenses 125B and 125C results in r=r_(B), whichindicates that the symmetric lens set 125 provides no magnification(e.g., provides zero magnification compensation). In FIG. 3C, a beamexits the lens 125C and converges toward and then passes the line 315. Adistance between the line 310 and the line 330 at an output of the lens125C is denoted by r_(C). In this regard, the gap between the lenses125B and 125C results in r>r_(C), which indicates that the symmetricmagnification lens set 125 decreases magnification. A decrease inmagnification may be quantified by a negative magnificationcompensation.

Although the description of FIGS. 3A-3C is with reference to the lenses125A-C of the symmetric magnification lens set 125, similar descriptiongenerally applies for the lenses 130A-C of the asymmetric magnificationlens set 130.

FIG. 4A illustrates an example cross-sectional view of the lenses 125A-Cin accordance with one or more embodiments of the present disclosure.FIG. 4B illustrates an example cross-sectional view of the lenses 130A-Cin accordance with one or more embodiments of the present disclosure.

In an embodiment, magnification lens sets (e.g., 125, 130) may bedesigned such that the magnification lens set can selectively add acontrollable amount of power into an optical system (e.g., 100) tochange a magnification associated with the optical system, as would beunderstood by a person of ordinary skill in the art. As an example, fora thin lens group of two lenses, a combination of thin lens power(denoted as φ′_(ab)) can be calculated as follows:φ′_(ab)= ′_(a)+φ′_(b) −dφ′ _(a)φ′_(b)where φ′_(a) is a first lens power, φ′_(b) is a second lens power, and dis a distance between the first and second lenses. If φ′_(a)=φ′_(b),then φ′_(ab)=dφ′_(a) ². Thus, in this case, the thin magnification lensgroup has zero power when the lens gap (e.g., lens air gap) is zero(i.e., d=0). The power of the magnification lens group increases whenthe lens gap increases.

Since d is a positive value, this magnification lens group createspositive power. In an aspect, in order for a magnification lens togenerate positive or negative magnification correction, another thinlens group with opposite (e.g., and equal) lens power can be employed,so magnification lens group power of the two lens groups is as follows:φ′_(ab)=φ′_(a)+φ′_(b) −d ₁φ′_(a)φ′_(a)φ′_(b)−(φ′_(a)+φ′_(b) −d₂φ′_(a)φ′_(b))where d₁ is a distance between the two lenses of a first thin lens groupand d₂ is a distance between the two lenses of a second thin lens group.When d₁=d₂, φ′_(ab)=0. When d₁>d₂, φ′_(ab)>0. When d₁<d₂, φ′_(ab)<0. Inthis case, the magnification lens group has four thin lenses. The fourthin lenses may be three lenses if a middle two lenses is combined as abiconvex or biconcave lens. In an embodiment, the magnification lens set125 and/or 130 may include the first and second thin lens groups asprovided above. For example, for the magnification lens set 130, thedistance d₁ may represent a gap between the lens 130A and 130B, and thedistance d₂ may represent a gap between the lens 130B and 130C.

In the foregoing, φ′_(a)=−φ′_(b). In other cases, φ′_(a)≈−φ′_(b) (e.g.,first lens power is not equal in magnitude to second lens power). Inthese cases,

${{{when}\mspace{14mu} d} = \frac{{\varphi\prime}_{a} + {\varphi\prime}_{b}}{d\;{\varphi\prime}_{a}{\varphi\prime}_{b}}},{\varphi_{ab}^{\prime} = {{0.\mspace{14mu}{When}\mspace{14mu} d} > \frac{{\varphi\prime}_{a} + {\varphi\prime}_{b}}{d\;{\varphi\prime}_{a}{\varphi\prime}_{b}}}},{\varphi_{ab}^{\prime} < {0.\mspace{14mu}{When}\mspace{14mu} d} < \frac{{\varphi\prime}_{a} + {\varphi\prime}_{b}}{d\;{\varphi\prime}_{a}{\varphi\prime}_{b}}},{\varphi_{ab}^{\prime} > 0.}$

In some cases, a magnification lens set with more lenses may allow alarger magnification correction range (e.g., also referred to as amagnification compensation range). In this regard, three, four, or morelenses may be utilized in a magnification lens set when largermagnification correction range is desired, for example a magnificationcorrection range around or wider than +250 ppm. For example, themagnification lens set 125 includes the lenses 125A-C and in some casesmay provide a magnification correction range of around ±250 ppm. In somecases, two lens in a magnification lens set may be selected whenmagnification correction is generally within a relatively smaller range,for example a magnification correction range around or under 70 ppm(e.g., between −70 ppm and +70 ppm, between −70 ppm and 0, between 0 and+70 ppm, etc.). For instance, the additional lenses in a four lens group(e.g., relative to a two lens group) may introduce extra distortion intoan optical system. Thus, for a smaller desired magnification correctionrange, fewer lenses may be used such that distortion is smaller.

In an embodiment, the optical system 100 (and/or other optical systems)may be utilized in a stepper lithography tool or a scanner lithographytool. For example, the optical system 100 may be employed on a Dysonlens system that is used in a stepper or a scanner. In an aspect, whenused on a stepper, a full field is exposed at one time. In the stepper,the field generally has a rectangular shape. The symmetric magnificationlens set 125 and asymmetric magnification lens set 130 may be utilizedto adjust a magnification of (e.g., apply magnification compensation to)the field. As the field is stepped over to a next site, the stepdistance varies to achieve magnification across a wafer. In a steppertool the field of view (FOV) is smaller than the wafer, so the steppertool steps the FOV across the wafer. Each step is considered a site. Insome cases, when using such magnification adjustment in a stepper tool,the magnification can be set for the average magnification across thewhole wafer. In other cases, when using such magnification adjustment ina stepper tool, the magnification setting may be adjusted to an averagemagnification of the field being exposed, and the magnification settingmay be adjusted as the wafer is moved from site to site.

The asymmetric magnification lens set 130 may be utilized to achieveasymmetric magnification. The asymmetric magnification lens set 130 maybe oriented to provide magnification s compensation along one axis ofthe scanner's FOV (e.g., magnification compensation in either thex-direction or the y-direction). In an embodiment, the asymmetricmagnification lens set 130 is oriented to create an asymmetricmagnification normal to a scanning direction. For example, the scanningdirection may be the x-direction, and the magnification compensation maybe applied in the y-direction.

In operation, the symmetric magnification lens set 125 may providesymmetric magnification compensation in both the x- and y-directionsacross the scanner's FOV, whereas the asymmetric magnification lens set130 may provide magnification compensation in the y-direction. Anexample range of the symmetric magnification compensation may be around±250 ppm, and an example range of the asymmetric magnificationcompensation may be around ±50 ppm (e.g., in the y-direction). In thisregard, any symmetric magnification compensation between +250 ppm and−250 ppm may be achieved, and any asymmetric magnification compensationbetween +50 ppm and −50 ppm may be achieved. These example rangesprovide the following extremes, in which X and Y are the nominalx-direction magnification and nominal y-direction magnification of theoptical system 100 (e.g., with zero magnification compensation in the x-and y-directions):

Extreme 1: Maximum Symmetric Magnification Compensation+MaximumAsymmetric Magnification CompensationX+250 ppm, Y+300 ppm

Extreme 2: Maximum Symmetric Magnification Compensation+MinimumAsymmetric Magnification CompensationX+250 ppm, Y+200 ppm

Extreme 3: Minimum Symmetric Magnification Compensation+MaximumAsymmetric Magnification CompensationX−250 ppm, Y−200 ppm

Extreme 4: Minimum Symmetric Magnification Compensation+MinimumAsymmetric Magnification CompensationX−250 ppm, Y−300 ppm

In some cases, small modifications to the optical and mechanical designmay be utilized to adjust the amount of symmetric magnification and/orasymmetric magnification without changing the primary design of anoptical system. For example, small modifications to the optical andmechanical design may be utilized to increase or decrease the amount ofsymmetric and asymmetric magnification without change to the primarydesign. Such small modifications may include adjusting the radii of themagnification compensation lenses and increasing or decreasing a travelof the lenses. In some cases, orders of two to three times those of thedesigned magnification can be achieved.

Although FIGS. 1 through 4 are described with reference to two sets oflenses with three lenses each, each set of lenses may have fewer, more,and/or different lenses than those shown in FIGS. 1 through 4. Inaddition, whereas FIGS. 1 through 4 provide example embodiments in whichone set of lenses may be configured to (e.g., designed to) providesymmetric magnification and another set of lenses may be configured toprovide asymmetric magnification, more and/or different sets of lensesmay be utilized in other embodiments to provide symmetric and/orasymmetric magnification. As one example, in another embodiment, anoptical system can include two asymmetric cylindrical lens assemblies.In some cases, such an optical system would ideally align the two lenssets orthogonal to one another, where one set of lenses along X formagnification of +250 ppm in the x-direction and the second set oflenses along Y for magnification of +250 ppm in the y-direction.

FIG. 5 illustrates a lens duo 500 of an optical system in accordancewith one or more embodiments of the present disclosure. The lens duo 500includes a lens 505 and a lens 510. The lenses 505 and 510 may bealigned such that the lenses 505 and 510 share an optical axis. Thelenses 505 and 510 are separated (e.g., by air) by a distance d alongthe z-direction. In FIG. 5, the lens duo 500 forms a symmetricmagnification lens set to provide rotational symmetric magnificationcompensation. As an example, the lenses 505 and 510 may be aplano-convex lens and a plano-concave lens, respectively. In anembodiment, the lens duo 500 may be used as the symmetric magnificationlens set 125 shown in FIG. 1.

A dashed line 515 depicts an optical path for a beam passing through anoptical axis of the lens duo 500 (e.g., an optical axis of the lenses505 and 510). A dashed line 520 is parallel to and displaced by adistance r from an optical axis along the x-direction. A solid line 525depicts an optical path for a beam entering through the lens 505 at adistance r from the line 515, converging toward the line 515 whenpassing through the air gap between the lenses 505 and 510, and passingthrough the lens 510 at a distance r₁=r−(Δx/Δy) from the optical axis.Since r>r₁, the lens duo 500 decreases magnification (e.g., provides anegative magnification compensation). To adjust the magnificationcompensation provided by the lens duo 500, one or both of the lens 505or the lens 510 may be movable. For example, the lenses 505 and/or 510may be moved by one or more actuators of an actuator system along thez-direction to adjust the distance d between the lenses 505 and 510.

In an aspect, with only one gap, the lens duo 500 of FIG. 5 generatesnegative or positive magnification compensation. This magnificationcompensation may be realized as defined previously for the case thatφ′_(a)≠−φ′_(b) (e.g., first lens power is not equal in magnitude tosecond lens power). Namely, in this case,

${{{when}\mspace{14mu} d} = \frac{{\varphi\prime}_{a} + {\varphi\prime}_{b}}{d\;{\varphi\prime}_{a}{\varphi\prime}_{b}}},{\varphi_{ab}^{\prime} = {{0.\mspace{14mu}{When}\mspace{14mu} d} > \frac{{\varphi\prime}_{a} + {\varphi\prime}_{b}}{d\;{\varphi\prime}_{a}{\varphi\prime}_{b}}}},{\varphi_{ab}^{\prime} < {0.\mspace{14mu}{When}\mspace{14mu} d} < \frac{{\varphi\prime}_{a} + {\varphi\prime}_{b}}{d\;{\varphi\prime}_{a}{\varphi\prime}_{b}}},{\varphi_{ab}^{\prime} > 0.}$When the lenses 505 and 510 have different radii, the magnification ofthe two lens group (denoted as φ′_(ab)) can be changed from positive tonegative for varying values of the gap d between the lenses 505 and 510.In some cases, use of a lens duo may be less expensive and/or result ina simpler product than use of a lens trio or more than three lenses.

Although the lens duo 500 of FIG. 5 form a symmetric magnification lensset, an optical system may employ a lens duo for an asymmetricmagnification lens set alternative to and/or in addition to employingthe lens duo 500. In this regard, the number of lenses in the symmetricmagnification lens set may be the same or may be different from thenumber of lenses in the asymmetric magnification lens set. The number oflenses used in an optical system may be based on considerations such ascosts, manufacturing complexity, performance specifications, and/orother considerations. In some cases, a lens duo may be associated withlower monetary costs and manufacturing complexity (e.g., than a lens setwith three or more lenses). In some cases, when the symmetricmagnification lens set and asymmetric magnification lens set eachinclude a lens duo, the mask may be undersized and/or oversized withasymmetry. For example, relative to a mask of a reference size, the maskmay be undersized by different factors and/or oversized by differentfactors at different portions of the mask.

In an embodiment, the asymmetric magnification lens set may be used toprovide asymmetric magnification compensation along only one direction(e.g., either x-axis or y-axis) and only one of positive magnificationcompensation or negative magnification compensation. For example, theasymmetric magnification lens set with two lenses may be used to correctone of the axes by anywhere between 0 to +50 ppm or 0 to −50 ppm asopposed to correcting one of the axes by anywhere between −50 ppm to +50ppm for an asymmetric magnification lens set with three (or more)lenses. In some case, the use of two lenses may be easier to manufacture(e.g., each lens of the two lens system may be made thicker). In somecases, the lens duo may be rotatable to allow magnification compensationalong one axis. For example, in one orientation of the lens duo, thelens duo may provide asymmetric magnification correction along only thex-axis. This lens duo may be rotated by 90° to provide magnificationcorrection along only the y-direction.

In some embodiments, the lenses 130A, 130B, and 130C of the asymmetricmagnification lens set 130 may be a plano-convex cylinder lens,concave-concave cylinder lens, and a convex-plano lens, with a thickestportion of the lenses 130A-C being around 2 mm to 10 mm. In an aspect, asingle lens may be employed in place of the lenses 130A, 130B, and 130C.FIG. 6 illustrates an asymmetric magnification lens 600 in accordancewith one or more embodiments of the present disclosure. In anembodiment, the asymmetric magnification lens set 130 may be theasymmetric magnification lens 600. In other embodiments, the asymmetricmagnification lens set 130 may include the asymmetric magnification lens600 along with one or more other lenses.

The asymmetric magnification lens 600 may be a plano window, such asshown in FIG. 6. An actuator may bend the asymmetric magnification lens600 to cause the plano window to deform into a concave-convex lens thatcan generate magnification compensation (e.g., along its bent axis).Depending on the direction that the asymmetric magnification lens 600 isbent, the asymmetric magnification lens 600 can create positive ornegative magnification compensation. In some cases, the asymmetricmagnification lens 600 may be selectively bent (e.g., deformed) in thex-direction, y-direction, or both as needed to create a desiredmagnification compensation (e.g., an asymmetric magnificationcompensation) in one or both of the x- or y-directions.

In an aspect, an actuator system may be provided to controlmagnification provided by the asymmetric magnification lens 600. Theactuator system may include an actuator 620, an actuator controller 625,and a feedback device 630. The actuator 620 may be configured to apply aforce along a set direction on the asymmetric magnification lens 600 toprovide magnification compensation in the x-direction, y-direction, orboth in accordance with control signals provided by the actuatorcontroller 625 to the actuator 620. The actuator controller 625 mayreceive information and generate these control signals for the actuator620 based on the received information. The information may be indicativeof a desired magnification to be provided by the asymmetricmagnification lens 600. In some cases, the control signals generated bythe actuator controller 625 may be indicative of a force (if any) to beapplied on the asymmetric magnification lens 600 by the actuator 620 anda direction to apply the force. By applying the force on the asymmetricmagnification lens 600, the actuator 620 may cause the asymmetricmagnification lens 600 to provide a desired magnification. The feedbackdevice 630 may be, may include, or may be a part of, an encoder;capacitive, inductive or laser sensor; strain gauge; and/or generallyany device that can be used to verify a configuration (e.g., amount ofbend, direction of bend, associated magnification) of the asymmetricmagnification lens 600 before, during, and/or after application of theforce by the actuator 620. In this regard, the actuator controller 625and feedback device 630 may operate in tandem (e.g., exchangeappropriate information) to help ensure the asymmetric magnificationlens 600 is configured properly. In some cases, the actuator 620, orother actuator, may rotate the asymmetric magnification lens 600alternative to or in addition to bending the asymmetric magnificationlens 600 to effectuate desired magnification compensation in thex-direction, y-direction, or both.

For example, the asymmetric magnification lens 600 may be bent by theactuator 620 (e.g., based on appropriate control signals from theactuator controller 625) to provide a lens 605 that causes positivemagnification compensation when light 615 travels in the oppositedirection as the bending direction. As another example, the asymmetriclens 600 may be bent by the actuator 620 to provide a lens 610 thatcauses negative magnification compensation when light 615 travels in thesame direction as the bending direction. When the asymmetricmagnification lens 600 is not bent, no magnification compensation isprovided by the asymmetric magnification lens 600. In an aspect, use ofa single lens, such as the asymmetric magnification lens 600, mayinvolve mechanical design and/or control complexity (e.g., associatedwith the bending) and may allow for easier manufacturing, smalleroptical thickness, and occupy less space in an optical system. In somecases, alternatively and/or in addition, a single symmetricmagnification lens that can be deformed to provide symmetric positivemagnification compensation or symmetric negative magnificationcompensation can be utilized as the symmetric magnification lens set.

FIG. 7 illustrates the beam steering lens 135 of the optical system 100in accordance with one or more embodiments of the present disclosure.The beam steering lens 135 may also be referred to as a tilting lens.The beam steering lens 135 may be tilted (e.g., by an actuator of anactuator system) as appropriate to redirect a beam of light to a desiredlocation (e.g., on the image plane 110). For example, the beam steeringlens 135 may be coupled to an actuator system that can control the tiltof the beam steering lens 135. The actuator system may include anactuator 705, an actuator controller 710, and a feedback device 715,which may be implemented in the same or similar manner as correspondingactuator systems of FIGS. 2A, 2B, and 6. The tilt may be represented byone or more angles. An angle a may provide an amount of tilt along anx-direction. Another angle (not shown) may provide an amount of tiltalong a y-direction. In FIG. 7, the tilt of the beam steering lens 135causes a displacement of a beam by a distance (Δx/Δy) relative to a casethat the beam steering lens 135 is not tilted. As shown in FIG. 7, thedisplacement of the beam by the beam steering lens 135 is based on thetilt angle or angles of the beam steering lens 135 and dimensions of thebeam steering lens 135 (e.g., a distance within the beam steering lens135 through which a beam needs to propagate).

FIG. 8 illustrates a beam steering lens 800 and associated components inaccordance with one or more embodiments of the present disclosure. Notall of the depicted components may be required, however, and one or moreembodiments may include additional components not shown in FIG. 8.Variations in the arrangement and type of the components may be madewithout departing from the spirit or scope of the claims as set forthherein. Additional, fewer, and/or different components may be provided.In an embodiment, the optical system 100 may be utilized to provideoptical asymmetric magnification with beam steering. In an embodiment,the beam steering lens 800 may be the beam steering lens 135.

The beam steering lens 800 may be supported in annular housing 805 and825. The annular housing 805 has a pivot shaft 810 that allows the beamsteering lens 800 to rotate in a first direction (e.g., x-direction). Aflexure member 812 is connected to the annular housing 805. A lineardrive 815 includes a voice coil actuator 820, ball slide assembly (notshown), and linear encoder. The voice coil actuator 820 may be coupledto the flexure member 812 and may displace the flexure member 812 by alinear axis to cause rotation of the beam steering lens 800. The linearencoder of the linear drive 815 may provide feedback to the voice coilactuator 820 and/or the ball slide assembly to control displacementand/or rotation of the beam steering lens 800 effectuated by the lineardrive 815.

The annular housing 825 of the beam steering lens 800 may facilitatetilting of the beam steering lens 800 in a second axis. For example, thesecond axis may be orthogonal to the first axis. The annular housing 825is coupled to the annular housing 805. The annular housing 825 has apivot shaft 830. The pivot shaft 830 is attached to a flexure member 835and a linear drive 840. The linear drive 840 includes a voice coilactuator 845, ball slide assembly (not shown), and linear encoder 850.The voice coil actuator 845 may be coupled to the flexure member 835 andmay displace the flexure member 835 by a linear axis to cause rotationof the beam steering lens 800. The linear encoder 850 may providefeedback to the voice coil actuator 845 and/or the ball slide assemblyof the linear drive 840 to control displacement and/or rotation of thebeam steering lens 800 effectuated by the linear drive 840.

Although FIG. 8 illustrates an example of a beam steering lens andassociated components (e.g., for mechanically displacing and/or rotatingthe beam steering lens), other beam steering lenses and/or associatedcomponents may be employed. For example, the voice coil actuators 820and/or 845 may be replaced with or used in addition to mechanical orpneumatic linear actuators and/or piezo stepping actuators. As anotherexample, the ball slide assemblies may be crossed roller slides. In someaspects, a beam steering lens may be tilted using a cam that is attachedto a rotary motor. In some aspects, an axis of the beam steering lensmay be driven directly using a rotary motor and/or a geared motor.

In some embodiments, a beam steering lens (e.g., 135, 700, 800) may beutilized with one or more lens sets described in the present disclosure,such as those shown in FIGS. 1-6. In some aspects, a beam steering lensmay be utilized with one or more lens sets, such as one or moresymmetric magnification lens sets (e.g., 125) and/or one or moreasymmetric magnification lens sets (e.g., 130). For example, withreference to FIG. 1, the beam steering lens 135 may be utilized with thesymmetric magnification lens set 125 (e.g., without the asymmetricmagnification lens set 130), or the beam steering lens 135 may beutilized with the asymmetric magnification lens set 130 (e.g., withoutthe symmetric magnification lens set 125).

Such modification to the optical system 100 of FIG. 1 to remove one ofthe magnification lens sets 125 or 130 may be associated withappropriate adjustment (e.g., positioning) of one or more associatedcomponents, such as the prisms 140 and 145 and the lens 160, 165, 170,and 175, or no adjustment of any of these components. As an example,consider the asymmetric magnification lens set 130 is removed from theoptical system 100. In one case, as previously described, the symmetricmagnification lens set 125; prisms 140 and 145; lenses 160, 165, 170,and 175; and mirror 155 may remain as shown in FIG. 1. An output beamfrom the prism 145 may be provided (e.g., as the beam 120) to the beamsteering lens 135 and directed onto the image plane 110. In anothercase, the symmetric magnification lens set 125 may be positioned wherethe asymmetric magnification lens set 130 is shown in FIG. 1, while theprisms 140 and 145; lenses 160, 165, 170, and 175; and mirror 155 mayremain as shown in FIG. 1. An output beam from the symmetricmagnification lens set 125 may be provided to the beam steering lens 135and directed onto the image plane 110. In yet another case, thesymmetric magnification lens set 125 may be positioned elsewhere, suchas between the prisms 140 and 145. Other manners by which to provide thesymmetric magnification lens set 125 and not the asymmetricmagnification lens set 130 may be utilized.

In one or more embodiments, the optical system may be, may include, ormay be a part of a projection lens system, used in a lithography system.FIG. 9 illustrates a lithography system 900 in accordance with one ormore embodiments of the present disclosure. Not all of the depictedcomponents may be required, however, and one or more embodiments mayinclude additional components not shown in FIG. 9. Variations in thearrangement and type of the components may be made without departingfrom the spirit or scope of the claims as set forth herein. Additional,fewer, and/or different components may be provided. In an embodiment,the optical system 100 may be utilized to provide optical asymmetricmagnification with beam steering.

The lithography system 900 includes a radiation source 905, mirrors 910and 915, a mask 925, an optical system 930, a wafer 935, and an airbearing stage 940. In FIG. 9, the mirrors 910 and 915 are opticalcomponents utilized to direct the radiation (e.g., UV light) from theradiation source 905 to the mask 925. Fewer, more, and/or differentoptical components may be provided between the radiation source 905 andthe mask 925. For example, additional optical components, such asoptical waveguides, lenses, and mirrors, may be between the mirrors 910and 915. In some cases, the mirrors 910 and 915 and/or other opticalcomponents may adjust beam characteristics of the radiation from theradiation source 905, such as optical distance (e.g., distances traveledby radiation from the radiation source 905 to reach the mask 925), beamshape, beam size, beam polarization, etc. The mask 925 may be disposedat an object plane of the lithography system 900, and the wafer 935 maybe disposed at an image plane 110 of the lithography system 900, withthe lithography system 900 being utilized to project a pattern on themask 925 onto the wafer 935 using the optical system 930. In thisregard, the optical system 930 may provide symmetric and/or asymmetricmagnification. In an embodiment, the optical system 930 may be, mayinclude, or may be a part of, the optical system 100 of FIG. 1. In thisembodiment, the mask 925 is disposed at the object plane 105 and thewafer 935 is disposed at the image plane 110.

In some embodiments, the lithography system 900 may be, may include, ormay be a part of, a scanning lithography machine. For example, FIG. 10illustrates a scanning lithography machine or portion thereof inaccordance with one or more embodiments of the present disclosure.

In this embodiment, the wafer 935 and mask 925 may both be mounted to acarriage that is scanned under the optical system 930 at a translationstage. The wafer 935 and mask 925 may be aligned to one another beforethe scanning process. The alignment process may involve translatingand/or rotating the wafer 935 relative to the mask 925, and may beperformed with a wafer positioning stage.

FIGS. 11A and 11B illustrate examples of exposure fields for a scanninglithography machine. An exposure field represents a FOV of a scanner ofthe lithography system 900. The exposure field moves across the wafer935 along an x-direction and displaces along a y-direction and reversesthe x-direction after reaching a turning point, as shown in FIGS. 11Aand 11B. In some cases, scans that are adjacent in time may overlap tohelp produce a uniform exposure across the wafer 935. In FIG. 11A, theexposure field (e.g., 1105) has a diamond shape. In FIG. 11B, theexposure field has a hexagon shape. In some cases, use of a hexagonexposure field may decrease time needed to scan the wafer 935 byincreasing a step distance in between scan passes. In this regard, thehexagon shape allows for a decreased overlapped area, which allows for areduced number of scan passes a higher machine throughput. Although thefollowing description is provided with respect to a diamond shapedexposure field, other exposure field shapes, such as the hexagon shape,rectangular shape, etc. may be utilized.

In some embodiments, a size of the exposure field (e.g., diamond shaped,hexagon shaped, etc.) may need to be adjusted during the scan across thewafer 935, and/or a location at which the exposure field impinges on thewafer 935 may need to be steered. FIG. 12 illustrates actual and desireddie size and location for various die on the wafer 935. In FIG. 12, thesame magnification is associated with each portion of the wafer 935 andthe same (or no) beam steering is associated with the wafer 935. Theactual die size and location overlay the desired die size and location.A die 1205 (e.g., a center die of the wafer 935) is an actual die sizeand location, whereas a die 1210 is its corresponding desired die sizeand location for the die 1205. Similarly, a die 1215 is an actual diesize and location, whereas a die 1220 is its corresponding desired diesize and location for the die 1215.

FIG. 13A provides an enlarged view of the die 1205 and die 1210 of FIG.12. To obtain the die 1210, the die 1205 may remain at the samelocation, but with positive magnification compensation applied toprovide a larger projection on the wafer 935. FIG. 13B provides anenlarged view of the die 1215 and die 1220 of FIG. 12. To obtain the die1220, positive magnification compensation and a shift of an image may beapplied. With reference to FIG. 1, the positive magnificationcompensation may be provided by the symmetric lens set 125 and/or theasymmetric lens set 130, and the shift may be applied by the beamsteering lens 135.

In some cases, such magnification compensation and/or image steering maybe adjusted as the wafer 935 is translated back and forth under theexposure field. As previously indicated, one or more beam steeringlenses may be utilized to steer a location of an image that is formed atan image plane (e.g., at the wafer 935). Such a technique may bereferred to as optical beam steering. With regard to lithographyapplications, the optical beam steering may be utilized to tilt aprojected image of the mask 925 using a beam steering lens incoordination with wafer position. FIGS. 14A through 14C illustratetilting of a beam steering lens of an optical system 900 as the wafer935 is moved, in accordance with one or more embodiments of the presentdisclosure. With reference to FIGS. 12 and 14A through 14C, as the wafer935 scans from left to right, the beam may be tilted to project theimage further toward the left extremity of the wafer 935. As the wafer935 is scanned to the right from its position at FIG. 14A, a tiltprovided by the beam steering lens may be continually adjusted insynchronization with the motion of the wafer 935 and mask 925 (e.g.,which are locked together in a scanner system). When the wafer 935 isdirectly under the beam steering lens (e.g., at the center die) as shownin FIG. 14B, the beam steering lens may provide zero tilt. As the wafer935 continues to the right as shown in FIG. 14C, the beam steering lensis tilted to project the image to the right extremity of the wafer 935.With reference back to FIG. 7, the beam steering lens may allow tiltingalong one or both of the x- and y-axis. For instance, if the scan occursalong the x-direction, an x-axis tilting of the beam steering lens isperformed in synchronization with the wafer scanning motion along thex-direction. A y-axis tilting may be performed during the step betweenrows of the scan.

In some embodiments, alternatively and/or in addition to beam steeringusing one or more beam steering lenses, micro wafer positioning may beutilized. In micro wafer positioning, the position of the wafer relativeto the mask may be minutely adjusted as the wafer 935 is scanned acrossan optical system (e.g., with or without a beam steering lens). Whilethe wafer positioning stage maintains the relative positioning of themask 925 to the wafer 935 during the scanning exposure, the position ofthe wafer 935 may be driven in an axis of scanning while the translationstage is performing its scan path. As the wafer 935 is scanned in the+x-direction (e.g., to the right), the micro wafer positioning may shiftthe wafer 935 relative to the mask 925 in a coordinated manner with thetranslation stage. In this manner, the wafer 935 is continually movedrelative to the mask 925 during a scan row. When the translation stagesteps to a next row, the translation stage may perform a micro step toshift the wafer 935 relative to the mask 925 to adjust for an offset inthe y-direction. In some cases, micro wafer positioning may be performedby a wafer positioning controller that can adjust the position of thewafer relative to the position of the mask in order to shift a positionon the wafer 935 at which an image is formed on the wafer 935 by havingmoved the wafer 935. It should be noted that, although the foregoingdescription of the present disclosure refers to the x-axis and y-axis asthe scan axis and step axis, respectively, it is understood that theconventions could also be that the x-axis is the step axis and they-axis is the scan axis.

With reference back to FIG. 10, the wafer positioning stage can haveaccurate and stiff fine positioning actuators that can be used to effectthe micro wafer positioning described above. In some cases, mechanicalpiezo actuators with strain gauge feedback acting upon a mechanicalflexure system can be used to adjust the wafer position relative to themask while the translation stage is in motion scanning and stepping thewafer under the lens FOV.

For example, FIGS. 15A through 15D illustrate a position of a scannerexposure FOV and associated wafer position shifting in accordance withone or more embodiments of the present disclosure. FIG. 15A illustratesmicro wafer positioning at scan start, with the wafer 935 being shiftedin −x-direction (e.g., left) and −y-direction (e.g., down). FIG. 15Billustrates micro wafer positioning at scan end, with the wafer 935being shifted in +x-direction (e.g., right). FIG. 15C illustrates microwafer positioning at scan start, with the wafer 935 being shift in−x-direction and +y-direction. FIG. 15D illustrates micro waferpositioning at scan end, with the wafer 935 shifted in +x-direction.

In an embodiment, an actuator controller (e.g., 215 in FIG. 2) mayreceive information associated with a relative positioning of the mask925 and the wafer 935. In a lithography system, images of the mask 925and wafer 935 may be captured by camera systems to determine an expectedprojection of the mask 925 (e.g., pattern of the mask 925) onto thewafer 935. The expected projection may be used to determinemagnification compensation, beam steering, and/or micro waferpositioning needed to adjust from the expected projection to a desiredprojection. The actuator controller may generate control signalsassociated with the magnification compensation, beam steering, and/ormicro wafer positioning and provide these control signals to relevantcomponents to effectuate the magnification compensation (e.g., actuators205 and 210 of the lens sets 125 and 130), beam steering (e.g., actuatorof the beam steering lens 135), and/or micro wafer positioning. FIGS.14A-14C and FIGS. 15A-15D depict the effectuation of the magnificationcompensation, beam steering, and/or micro wafer positioning.

In an embodiment, as an example, the wafer 935 may be moved (e.g., usingan actuator system) at a constant velocity relative to the mask 925 inan alternating fashion for each scan pass. For example, with referenceto FIGS. 2A and 9, to achieve a target magnification of 200 ppm, theactuator 205 may move the symmetric magnification lens set 125 to aposition associated with providing a magnification of 200 ppm and thenthe wafer 935 would scan relative to the mask 925 on each scan pass anamount equal to 200 ppm across the wafer 935. For smaller magnificationamounts, the shift may generally be smaller. An associated velocity maybe defined by a shift amount (e.g., based on magnification amount)divided by a time to complete the scan pass. In this regard, a smallertarget magnification (e.g., 50 ppm) may utilize a smaller shift and thushave a smaller velocity, relative to a larger target magnification(e.g., 200 ppm) that has a larger shift and thus a higher velocity. Fora given magnification, the velocity is constant.

In an embodiment, an additional use of beam steering and/or micro waferpositioning can be to compensate for small translation or rotationaldifferences between the mask and wafer that are identified during thealignment routine. For example, if the wafer is translated relative tothe mask, the wafer can be repositioned to be directly under the mask,or the beam steering can be utilized to compensate for the offset. Thiscan be applied to rotational differences as well. It can also be appliedin cases where there is a different correction required in thex-direction and the y-direction for the alignment.

Software in accordance with the present disclosure, such asnon-transitory instructions, program code, and/or data, can be stored onone or more non-transitory machine readable mediums. It is alsocontemplated that software identified herein can be implemented usingone or more general purpose or specific purpose computers and/orcomputer systems, networked and/or otherwise. Where applicable, theordering of various steps described herein can be changed, combined intocomposite steps, and/or separated into sub-steps to provide featuresdescribed herein.

The foregoing description is not intended to limit the presentdisclosure to the precise forms or particular fields of use disclosed.Embodiments described above illustrate but do not limit the invention.It is contemplated that various alternate embodiments and/ormodifications to the present invention, whether explicitly described orimplied herein, are possible in light of the disclosure. Accordingly,the scope of the invention is defined only by the following claims.

The invention claimed is:
 1. An optical system comprising: a lens systemconfigured to receive first radiation associated with an object anddirect second radiation associated with an image of the object toward animage plane disposed on a wafer, the lens system comprising: a first setof lenses configured to receive and selectively magnify the firstradiation to obtain first selectively magnified radiation; a first prismconfigured to receive the first selectively magnified radiation from thefirst set of lenses, wherein the first set of lenses is positionedbetween the first prism and the object and has a surface facing theobject and a surface facing the first prism; an actuator systemconfigured to: selectively adjust the first set of lenses to adjust amagnification associated with the image; and in response to one or morecontrol signals, adjust a tilt of a beam steering lens as the wafer isscanned; and the beam steering lens configured to direct, based at leaston the tilt of the beam steering lens, the first selectively magnifiedradiation to provide the second radiation.
 2. The optical system ofclaim 1, further comprising: a mirror configured to receive the firstselectively magnified radiation from the first prism and reflect thefirst selectively magnified radiation; and a second prism configured toreceive the first selectively magnified radiation reflected from themirror and direct the first selectively magnified radiation on anoptical path toward the beam steering lens and the image plane.
 3. Theoptical system of claim 2, further comprising a lens assembly, whereinthe mirror is configured to receive the first selectively magnifiedradiation from the first prism via the lens assembly, wherein the secondprism is configured to receive the first selectively magnified radiationreflected from the mirror via the lens assembly, wherein the lensassembly comprises a plano-convex lens and a meniscus lens, wherein theplano-convex lens has a surface facing the first and second prisms, andwherein the meniscus lens has a surface facing the mirror.
 4. Theoptical system of claim 2, further comprising a second set of lensesbetween the beam steering lens and the second prism, wherein the secondset of lenses has a surface facing the second prism and a surface facingthe beam steering lens.
 5. The optical system of claim 4, wherein thesecond set of lenses is configured to provide a magnificationcompensation range that is smaller than a magnification compensationrange provided by the first set of lenses.
 6. The optical system ofclaim 1, further comprising a second set of lenses configured to receiveand selectively magnify the first selectively magnified radiation toobtain second selectively magnified radiation, wherein the actuatorsystem is further configured to selectively adjust the second set oflenses to asymmetrically adjust the magnification in a first directionand a second direction, and wherein the beam steering lens is configuredto direct, based at least on the tilt of the beam steering lens, thesecond selectively magnified radiation to provide the second radiation.7. The optical system of claim 6, wherein: the actuator system isconfigured to adjust the second set of lenses to apply a firstmagnification compensation value along the first direction to themagnification and to apply a second magnification compensation valuealong the second direction to the magnification; and the firstmagnification compensation value is different from the secondmagnification compensation value.
 8. The optical system of claim 1,wherein: the optical system is a lithography system; the objectcomprises a pattern of a mask; and the image comprises a projection ofthe object on the wafer.
 9. The optical system of claim 8, furthercomprising: a magnification controller configured to generate the one ormore control signals, wherein the one or more control signals areassociated with an adjustment of the tilt of the beam steering lens andassociated with an adjustment to the magnification based at least on aposition of the mask relative to a position of the wafer, and whereinthe actuator system is configured to receive the one or more controlsignals and cause adjustment of the magnification in response to the oneor more control signals; and a wafer positioning controller configuredto adjust the position of the wafer relative to the position of the maskto shift a position of the image on the wafer.
 10. The optical system ofclaim 8, wherein: the lens system is configured to project a respectiveportion of the pattern onto a respective portion of the wafer; theactuator system is configured to, in response to the one or more controlsignals, adjust the tilt of the beam steering lens further incoordination with movement of the wafer; and each portion of the waferis associated with a respective tilt of the beam steering lens.
 11. Amethod comprising: receiving first radiation associated with an object;directing the first radiation through at least a first set of lenses anda first prism to obtain second radiation, wherein, during the directingthe first radiation, selectively adjusting the first set of lenses toadjust a magnification associated with an image of the object, andwherein the first set of lenses is positioned between the first prismand the object and has a surface facing the object and a surface facingthe first prism; and directing the second radiation toward an imageplane disposed on a wafer by adjusting a tilt of a beam steering lens asthe wafer is scanned.
 12. The method of claim 11, wherein the directingthe first radiation comprises directing the first radiation through atleast the first set of lenses, the first prism, and a second set oflenses to obtain the second radiation, wherein, during the directing thefirst radiation, selectively adjusting the second set of lenses toasymmetrically adjust the magnification in a first direction and asecond direction.
 13. The method of claim 12, wherein the selectivelyadjusting the second set of lenses comprises selectively adjusting thesecond set of lenses to apply a first magnification compensation valuealong the first direction to the magnification and to apply a secondmagnification compensation value different from the first magnificationcompensation value along the second direction to the magnification, andwherein the first direction is orthogonal to the second direction. 14.The method of claim 12, wherein the directing the first radiationcomprises: directing the first radiation through the first set of lensesto the first prism to obtain a first selectively magnified radiation;directing the first selectively magnified radiation by the first prismto a mirror; reflecting the first selectively magnified radiation by themirror to a second prism; and directing the first selectively magnifiedradiation by the second prism through the second set of lenses to obtainthe second radiation.
 15. The method of claim 11, wherein: the objectcomprises a pattern of a mask; the image comprises a projection of theobject on the wafer; and the directing the second radiation comprisesprojecting each portion of the pattern onto a respective portion of thewafer.
 16. An optical system comprising: a lens system configured toreceive first radiation associated with an object and direct secondradiation associated with an image of the object toward an image plane,the lens system comprising: a first set of lenses configured to receiveand selectively magnify the first radiation to obtain a firstselectively magnified radiation; a second set of lenses configured to:receive and selectively magnify the first selectively magnifiedradiation to obtain the second radiation; and direct the secondradiation toward the image plane; and an actuator system configured toselectively adjust the first set of lenses and/or the second set oflenses to adjust a magnification associated with the image along atleast one of a first direction or a second direction, wherein one set ofthe first set of lenses or the second set of lenses is configured toasymmetrically adjust the magnification in the first and seconddirections, and wherein an other set of the first set of lenses or thesecond set of lenses is configured to symmetrically adjust themagnification in the first and second directions.
 17. The optical systemof claim 16, further comprising a beam steering lens configured toreceive the second radiation from the second set of lenses and directthe second radiation toward the image plane based at least on a tilt ofthe beam steering lens, wherein the tilt of the beam steering lens isadjustable by the actuator system, and wherein the first direction isorthogonal to the second direction.
 18. The optical system of claim 16,further comprising: a first prism configured to pass the firstselectively magnified radiation; a mirror configured to receive thefirst selectively magnified radiation from the first prism and reflectthe first selectively magnified radiation; and a second prism configuredto receive the first selectively magnified radiation reflected from themirror and direct the first selectively magnified radiation to thesecond set of lenses.
 19. The optical system of claim 16, wherein: theactuator system is configured to adjust the second set of lenses toapply a first magnification compensation value along the first directionto the magnification and to apply a second magnification compensationvalue along the second direction to the magnification; and the firstmagnification compensation value is different from the secondmagnification compensation value.
 20. The optical system of claim 16,wherein: the optical system is a lithography system; the objectcomprises a pattern of a mask; the image plane comprises a wafer; andthe image comprises a projection of the object on the wafer.